A169947 Third entry in row n of triangle in A169945.

1, 3, 8, 16, 29, 49, 82, 130, 205, 305, 450, 654, 947, 1343, 1902, 2648, 3675, 5015, 6824, 9166, 12343, 16393, 21762, 28682, 37695, 49055, 63892, 82610, 106691, 136643, 174862, 222524, 283073, 357691, 451538, 567498, 712817, 890365, 1112040, 1382374, 1717497

Offset: 1

Author

N. J. A. Sloane, Aug 01 2010

Keywords

• nonn

Links

• Fausto A. C. Cariboni, Table of n, a(n) for n = 1..99 (terms 1..64 from Alois P. Heinz)
• Index entries for sequences related to carryless arithmetic

Crossrefs

Related to thickness: A169940-A169954, A061909.

Programs

Mathematica

b[n_, s_] := Module[{sn, m}, If[n<1, 1, sn = Append[s, n]; m = Length[sn]; If[m*(m - 1)/2 == Length[Table[sn[[i]] - sn[[j]], {i, 1, m - 1}, {j, i+1, m}] // Flatten // Union], b[n - 1, sn], 0] + b[n - 1, s]]];
c[n_] := c[n] = b[n - 1, {n}] + If[n == 0, 0, c[n - 1]];
a[n_] := c[n + 1] - n - 2;
Table[Print[n, " ", a[n]]; a[n], {n, 1, 64}] (* Jean-François Alcover, Sep 02 2019, after Alois P. Heinz in A143823 *)

Formula

Wanted: a recurrence. Are any of A169940-A169954 related to any other entries in the OEIS?

a(n) = A143823(n+1) - n - 2. - Nathaniel Johnston, Nov 12 2010

Extensions

More terms from R. J. Mathar, Aug 02 2010

a(22)-a(28) from Nathaniel Johnston, Nov 12 2010

More terms from Alois P. Heinz, Sep 16 2011